We have developed a TBC for Gas Turbine Engines application, and we have outstanding results regarding thermal test as well as adhesion strngth. We have tried every method to pileup coating from substrate but not succeed. Might be due to the interlocking bond at the interface is very good, We want to do study about this, why this happed. Guide me for the same. Coating can also resist at 1400 C temperature.
Note: Coating was developed by using lab synthesized nano YSZ particles (spray dried) as feed stock in APS. MCrAlY was used as bond coat.
Dear Amit,
I know everything what you said. All examinations already have been done. We didnt find a specific reason for good adhesion strength and good thermal shock resistance.
It's more than 40 years known why the YSZ TBC possess good thermal shock resistance: through the porous and cracked microstructure is the elasticity module of these layers extremely low. A low E-modulus automatically means a good thermal shock resistance (it can not form a large mechanical stresses in the layer). The so-called "nano-TBC" are still porous and weaker than normal, so no wonder.
Unfortunately, the low strength is responsible for a very low resistance to erosion, which must withstand the turbine blades.
The term "good adhesion" is far too optimistic in terms of YSZ layers. Is 10 to 20 MPa, a good adhesion? For some other layers, it would be very bad. But 10-20 MPa corresponds to the tensile strength of TBC, which means that the cohesion and adhesion are close to equal (adhesion is so very good because could not be better!).
1400°C is not a critical temperature for a compact YSZ, but way too much for a plasma-sprayed layer. A realistic temperature at the surface of YSZ top coat is now at about 1200°C. Temperature at the interface between bond coat and top coat must in duration not exceed 950°C.
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